This is divided into two seperate bodges, bodge (a), and bobdge (b), as you
will be
aware a true bodger moves swiftly from one cock-up to another, unphased by
his
complete lack of competence :O)
Bodge (a).
----------
With the aid of a signal booster (4 way as it happens), I had been enjoying
watching TV (on my Television) via my Freeview box and also on my PC
via a Freecom (DVB) USB stick.
Not satisfied with this happy state of affairs I thought why not move the
signal
booster out of the living room up into the loft, where it would be 'out of
the way'
and also able to power the aerial socket in the kitchen (unconnected at the
time).
I figured that I could use a passive splitter in the living room once the
signal
was being boosted from the loft.
I just ran an extennsion cable to the loft for power to make things 'easy'.
Anyway I put the booster in the loft so it was powing the two down leads.
When I tried to use the passive splitter I had in the living room I found
that only one of the 'ports' was working, as I had no other splitter
I decided to 'make one myself' by combining some cables (none of the
impedance matching bull for me!!) anyway as I was trying to connect this up
I (at come point) felt a 'tingling' feeling in my fingers. That doesn't feel
right
I though, so I went and got the booster from the loft and tried it in its
previous
configutation in the living room and as I suspected it was no longer working
(although its blue light was on and the fuse was not blown).
Actually I am not 100% sure it is buggered, cos some of the cables I made up
can be a bit dodgy. However I just tested it again it is buggered, it will
let a signal through
albeit a bad one, worse than unboosted. Interestingly the gain controls
still works,
it varies from a crap picture to an abysmal on (testing on analogue).
(I might have a go at fixing that later).
So I am now wondering what caused it to blow? I rechecked my cable,
especially looking
for 'earth to signal' 'shorts but the cable seemed fine, the main problem
with these cables
is asembling the connectors on them and not getting an open circuit on the
signal.
Anyway down to just an unboosted signal I tired to see if my signal splitter
cable
would work anyway, it turns out it did at least on the strongest muxes but
no chance
on the weaker ones as I expected. Dunnno if a propper spliitter would have
faired any
better.
Anyway I also got the 'tingling' sensation when fiddling with the splitter
cable soI am wondering what is going on?
There is no booster so the energy is not coming from there so that leaves
just the
USB stick or the Freeview box. I am not 100% sure exactly when I got the
tingling
but I think it was when touching the earths shields of two different cables.
Lets
face it you can only really tough the earths, not the signal because it is
inside.
So I am figuring there is a difference between the two earths or something?
Actually it would have to be quite a big difference wouldn't it? I mean
You don't get a tingling from say, a 9 volt battery do you, rather
worrying!!
Actually I am going get my voltmeter out right now and test the two earths
potential differences!! I might be in for a shock! Quite literally!!
Hmmmm..interesting I am recording a 4-5 volt difference between the two
earths!!
Perhaps more to the point, I noticed that 'at first contact' on one of the
tests it
appeared to register 18 volts!!! (and then drop back to 4-5 volts) is this
normal?
Incidently the tingle I experienced in my fingers gave me the impression it
was high
voltage, similar to something I experience from a faulty light switch
(nothinig to do
with me I might add!!), seems like there maybe some capacitive effect here?
I should add that the TV and PC are on different power sockets, but the
sockets
are probably on the same 'spur' or 'ring' they are in the same room anyway!!
I will try and connect them to the same socket to see if this that is any
better.
This leads me to another thought, the signal booster 'blew' when it was in
the loft,
powered from an upstairs socket, it never blew when it was down stairs, even
though
that 4-5 volt earth difference was present. Maybe the situation is even
worse with three
different sockets interacting? Also I wonder if I can take it back to the
shop
(Maplins) as faulty, I don't have the receipt though. As far as I can see it
'blew' whilst in
'normal usage'? I don't think my 'homemade' signal splitter can be blamed.
Another though is why my 'propper' signal splitter failed? Did it burn out
due to
some earth level problem? Or was it just because it was dirt cheap (a few
quid)
and shoddily made (very tight connector fittings requiring some force?).
Bodge (b).
----------
Moving on somewhat, undeterred by my recent failures I decided to try and
boost
the signal in the loft by adding another identical aerial, side by side with
the original
areial in the loft. I tried as well as I could (well I made an effort) to
keep the
aerials parallel and have the same length of cable to each aerial (about two
nine
inch lengths twisted on to the original length.
This however I had no success the resulting signal was worse, much worse!!
I could only get a very block picture on the best mux and nowt on the
others!!
I tried to adjust the aerials alignment a little but it made no difference.
Then I wondered
if it mattered which way around the earth and signal were connected to the
aerials.
The aerials recieve a vertical signal, I noticed that one had the earth
connected to the
top 'connector' and the other had the earth connected to the bottom
connector,
however I also noticed that one of the aerials was upside down so to speak,
in respect
to the other, such that it needed to be turned 180 degrees on its long axis
to be oriented
the same way. I though that these two 'errors' might cancel each other out
(if indeed it
mattered at all) and that the resulting two signals would be back 'in
phase', however
I am not too sure. Anyway I gave up at this point and went back to a single
aerial
as it was getting late. Any comments regarding me combining the two areials
like this? OK maybe I should have used a propper 'combiner' to match
impedances
or whatever, but the one I have doesn't work so I couldn't use that. I was
pretty disapointed
with the results I got, the first thing I thought is that the signals are
close to completely
out of phase, almost cancelling each other out, just how accurate do you
have to be?
What is the margin of error? My guess is the maximum difference the
alignment,
mounting and cabling could have ammounted to would be about 2 iinchs, but
probably a
lot less.
Anyway I will have another 'bash' at it tomorrow, this time I will measure
the cable lengths
accurately and make sure the aerials are orientated the same way with the
earths and signals
connected to the appropiate 'studs', incidently uk TV wavelengths are 40-80
cm (approx).
I am hoping I got my signals 180 degress out for phase with my first 'bash'
hoping for better
luck tomorrow. I am going to carry my portable TV in the loft as a 'signal
tester', hopefully
without breaking my neck.
Future plans
------------
I have put off adding a 'proper' powerpoint to the loft for the time being
for obvious
reasons :O)
I might have a go at fixing my signal booster some time, probably be cheaper
to buy
a new one though.
Maybe the diagram is simiilar to this? Probably the transistor thingy is
blown?
Fook knows.
http://www.zen22142.zen.co.uk/Circuits/rf/uhfpreamp.htm